MINIMAL IMPORTANT DIFFERENCE OF TWO METHODS FOR ASSESSMENT OF QUADRICEPS FEMORIS STRENGTH IN INDIVIDUALS WITH COPD

Abstract

<b>Background:</b> The assessment of quadriceps femoris (QF) strength is recommended by international guidelines as an outcome of exercise training (ET) programs in patients with chronic obstructive pulmonary disease (COPD). However, a value that represents its minimal important difference (MID) for different assessment methods has not yet been identified. <b>Aims:</b> To identify the MID of two methods for the assessment of improvement of QF strength after a high-intensity ET program in individuals with COPD: 1-repetition maximum (1RM) test and maximal voluntary contraction (MVC). <b>Methods:</b> Individuals with stable COPD were submitted to a high-intensity ET program composed by walking and cycling plus strengthening exercises (3 days/week for 3 months). Assessments of lung function, exercise capacity (6-minute walk test [6MWT]) and QF strength (1RM test performed in a multigym and MVC by using a strain-gauge) were performed before and after the ET program. <b>Results:</b> 21 individuals (11 males, 65±8 years, FEV1 51±16 %pred, 6MWT 478±56 meters) were studied. For the MVC, the MID calculated by distribution-based methods ranged from 9.4 to 16 Nm (or increase of 7.4% to 12.6% from baseline). For the 1RM test, MID values ranged from 2.5 to 3 kg (or increase of 12% to 15% from baseline). Anchor-based MIDs could not be calculated due to lack of correlation with the anchor (6MWT). <b>Conclusions:</b> According to distribution-based methods, the MID for improvement of quadriceps femoris strength after a high-intensity exercise training program in stable individuals with moderate-to-severe COPD ranges between 9.4 and 16 Nm for the MVC assessed with a strain gauge, and between 2.5 and 3 kg for the 1RM.